Re: Mercruiser Engine Problem
 

As other's have already mentioned here, my first guess would be a weak fuel pump. Hook up a fuel pressure gauge and take it out so you can see what it is reading under a load. I recently had the same problem. Fuel pressure was 40+ PSI at idle and dropped down to about 17 PSI as I started to plane the boat out. Good luck! I agree that the IAC would be a very unlikely culprit, but stranger things have happened!! Also, check the fuel line from the tank to the fuel filter housing and make sure it has not developed a soft spot and is collapsing under load.

Re: Mercruiser Engine Problem
 

My uncle had this problem 2 years ago, the Merc mechanic went through everything in the end it turned out to be plug wires. I'm still at a loss but the bad wires seemed to mess up the computer.

Last year the other motor started surging at idle, still haven't fixed that one.

If it were me I would be taking the advice the board has given and start swapping components from one motor to the other.

Re: Mercruiser Engine Problem
 

Youve been wrong other times, I wouldnt be so high and mighty if I were you.

Re: Mercruiser Engine Problem
 

i had nothing to do with this thread... do i still get in trouble???

Re: Mercruiser Engine Problem
 

hehe, you should have known better than post in the thread...now you're a culprit!

Re: Mercruiser Engine Problem
 

no this time its just me

Re: Mercruiser Engine Problem
 

[QUOTE=Edward R. Cozzi] YOU MIGHT AS WELL HAVE SUGGESTED HE TEST THE WINDSHIELD WIPER SWITCH!

QUOTE]


Funny You should say that......... It's a long story that I'll have to tell you sometime :D

Re: Mercruiser Engine Problem
 

stecz did it again

Re: Mercruiser Engine Problem
 

[QUOTE=CAP071]I would love to hear that sometime, provided I can share my stories with you!

Re: Mercruiser Engine Problem
 

you bad apple you........

Re: Mercruiser Engine Problem
 

ok ill go hide in the bildge under the motor

Re: Mercruiser Engine Problem
 

But not just before a sea trial!

Re: Mercruiser Engine Problem
 

:o

Re: Mercruiser Engine Problem
 

This thread literally disappeared yesterday... :rolleyes:

Now it's back... :eek:

Re: Mercruiser Engine Problem
 

its like an ugly girl, they keep coming back

Re: Mercruiser Engine Problem
 

Is now a good time to say the comment about checking the wiper motor switch was some funny chit? If bad timing, don't read this posting. :p

Re: Mercruiser Engine Problem
 

I'm having a similar problem with a carbed engine. It dies under load. It revs up fine and doen't miss a beat in neutral, but try to get on a plane, and it dies. I've about convinced myself it's the carb, so I plan on swapping them to see if the problem follows the carb. I just got to thinking the other day, that was the engine I had out for tranny work early this year. I wonder if a fuel line got kinked or bent when pulling the engine. I haven't looked yet.

Re: Mercruiser Engine Problem
 

cuda:
I worked on a SeaRay once with twin 4.3L that did the same thing. Finally found that the lagging engine had no spark advance. Joe, have you ever seen this?

Re: Mercruiser Engine Problem
 

Alpha outdrives? Shift interupter switch bad or maladjusted.

Re: Mercruiser Engine Problem
 

honestly not in a long time since the days of mech advance unless some one left a timming shunt in place (grounds the dist advance to set base timming )
or a bad comp...assuming thunder bolt ign

Re: Mercruiser Engine Problem
 

I had the same symptom, like someone turning the key on and off really fast, randomly and only under load.
I switched the port ignition module (cutting out side) with the starboard one. Then the starboard engine started cutting out. Defective ignition module. Replaced it and it ran fine.

Re: Mercruiser Engine Problem
 

if shift interupter will stall when put in to gear not once under way. more then likly its in the fuel system but could be one of many things.....

first to check would be filters and line, tend to think cuda is right on that its in the carb need to listen to how the motor sounds just before it dies, is it starving for fuel before dieing or just cut out abruptly

could be dist advance but havnt seen that in a looong time and normaly dont think that would stall it just give no power


but ive been wrong before

Re: Mercruiser Engine Problem
 

Ok, heres a good one. Back in the old days when the igntion circuit wiring circuit was protected by a fuse, I had a engine that would run for 15-20 minutes at wot and then drop dead. Wouldnt start for 15 minutes, then started and ran fine for another 15 -20 minutes at wot. If you ran at less than wot, it would run all day. Fuel problem of course, right? Not. And I wont go into all the time and effort I spent troubleshooting it. Turned out it was the damn fuse that was getting hot enough to go open (like a semiconductor) only when the ignition load was maxed. New fuse, problem stopped. That one taught me to never ever assume to know what was going on based on the symptoms.

Re: Mercruiser Engine Problem
 

You need to check your fuel pressure, ignition, etc., and check for codes. There could be something easily located with a scan tool. The iac (should I even touch this) can slow the engine down on some engines. However, not this one. In 1999 all power reduction capabilities are off according to merc. The computer still can be at fault with no codes. You have twins, swap computers or any other suspect parts and test run. Just don't change them all at the same time.

Re: Mercruiser Engine Problem
 

So my question is, If your windhield wipers stop working, should you check the IAC? :D :D

Re: Mercruiser Engine Problem
 

yes

Re: Mercruiser Engine Problem
 

NO! Darn you ,Joe!

Re: Mercruiser Engine Problem
 

and if the radio stops working check the tps

Re: Mercruiser Engine Problem
 

PROBLEM FIXED!!!!!!!!!!!!!!!!! Thank you to all who gave there expert advice. The problem ended up being this. I guess I heard from someone that Formula or shall we say Mercruiser has had many problems in the past with the same problem that I had. IT was coming from the fuel pump. So instead of them fixing the problem all the did was get a work around and they put this workaround in boats that came from the factory. All the formula boats now have a fuel pump BOOSTER or some call it a FUEL PRIMER. IT is between the fuel tank and the fuel filter. For some reason with this particular engine they were getting this on/off reaction under load with the fuel pump that they were using. So what they did is just add this fuel primer or Booster and that solved the problem. So located the booster took it out and found out that the motor was stuck on it. So basically the engine does not work good on its own fuel pump it needs this booster to help it work. So I just purchased a new one and when it arrives I will install and finally enjoy my boat. Thanks again to all who give advice.

Re: Mercruiser Engine Problem
 

merc also with that fix had a problem with the debris from the fuel tank clogging the screen on the booster pump and they came up with a bulletin that has a new pre filter so the pump does not burn up,

it was primarily for the 496 when it first came out if you want I can find the bulletin for you

Re: Mercruiser Engine Problem
 

here you go heres the bulletin...took me a few to find it

Re: Mercruiser Engine Problem
 

Thank you for the info. Also I wanted to know do you know where I can get that filter? Searched for it and could not find it anywhere. Thanks.

Re: Mercruiser Engine Problem
 

merc dealer should have it if not they can order itmost have the kit in 02 it was a retro fit for all 496s

Re: Mercruiser Engine Problem
 

in new boats the metal from when they made the fuel tanks and drilled the holes out that was left in the tanks was killing the boost pumps


be advised mercury is VERY VERY proud of those kits they sell for over 100.00 I think. Its a filter and a bunch of fittings to put the filter inline.

Re: Mercruiser Engine Problem
 

Joe:
Years ago I did an engine oil and filter change on this girl's Chevelle. That's ALL I did.

She came back screaming at me that I broke her cigarette lighter! True story.
Ed

Re: Mercruiser Engine Problem
 

Maybe she just really wanted a date? Kinda like leaving your car keys behind. ;)

Re: Mercruiser Engine Problem
 

think it was her way of saying she wanted a little.....


Happens all the time, (not that some 300 lb guy wants alittle)
......you changed my drive lube now the radio doesnt work what did you do...



dont know a tech anywhere that hasnt heard it atleast once or twice

Re: Mercruiser Engine Problem
 

Loose wire on my ignition. Same thing, only under load which is what threw be off. I guess the boat wasn't bouncing enough below 2000 RPM'S

Engine power
 

I've changed theSpark plugs, fuel filter, fuel filter to the carburetor the fuel pump and the fuel, and still it only starts and runs for 2 seconds after I pump the throttle, now I'm ordering a new coil pack, what do you think the problem could be. Prior to this when the problem first arrose, I was running fine and suddenly the I lost power for a minute and then it would regain, then die down and regain and that's how it continued to operate

What year and engine? Get a test light and start checking for voltages at the coil with key on and in run mode.